1. Field of the Invention
This invention relates to improved high-strength, fatigue resistant strands and wire ropes. This invention also relates to methods for making the strands and wire ropes.
2. Description of the Related Art
Strands and wire ropes are used in a wide range of applications for lifting and holding objects. For example, wire ropes are used in cranes as lifting elements and as pendants to support the boom. Most standard wire ropes comprise six outer strands surrounding a central core. Three-strand wire ropes are specifically designed to reduce rotation under load. These wire ropes have been used in tower cranes where torque generation in the ropes needs to be minimized for better rope performance.
Wire ropes are produced from various metals that can be drawn into small-diameter wire and have sufficient ductility for the forming process. Presently, high-carbon wires are used in strands and wire ropes. Other metals that are used include stainless steels, copper, aluminum and other alloys. The most commonly used materials for wire ropes are high-carbon steels and stainless steels. High-carbon steel wire ropes can be used in applications and environments in which corrosion is not a major concern. High-carbon steel wire ropes can be galvanized for corrosion resistance. In addition, high-carbon steel wire ropes can be compacted for use in applications requiring higher strength and improved crush resistance and fatigue life.
Desired properties for strands and wire ropes include high strength; high strength-to-weight ratio to reduce the weight of the wire rope having sufficient strength for a given use; high fatigue life to withstand repeated stresses; and suitable bending stiffness. In addition, reduced rotation under load is also desired for better performance.
There is a need for improved strands and wire ropes that have improved properties and can be provided in various material compositions. There is also a need for a method of making the improved strands and wire ropes.